Electrical energy comparison system and method



N. MARCHAND ELECTRICAL ENERGY COMPARISON SYSTEM AND`METHOD Filed July s,1945 April 26, 1949.

Patented Apr. 26, 1949 ELECTRICAL ENERGY COMPARISON SYSTEM AND METHODNathan Marchand, New York, N. Y., assignor to Federal' Telephone andRadio Corporation, New York, N. Y., a corporation of DelawareApplication July 3, 1945, Serial No. 602,952

7 Claims'. 1

The present invention relates -fto electrical energy systems andmethods.

For certain purposes the direct comparison or direct measurement of therelative amplitude of different electrical energies is diilicultaccurately to make and undesirable.

An object of the present invention is the provision of a method andmeans for indirectly comparing the relative amplitudes of separateelectrical energies. In accordance with an aspect of my invention, Iaccomplish this by translating the differences in amplitude intocorresponding diierences in phase and comparing the diierences of phase.

It is `a further object of my invention to provide a translation circuitthat. will translate dif-V ferences in amplitude of energy of the samefrequency into differences of phase.

In certain direction finders, there may be de rived from the antennasystem, two voltages approximately 90 out of phase, the relativeamplitudes of which when compared will indicate the direction from whicha signal is being received.

Another object of the present invention is the provision, in a directioniinder of the type described, Of means and a method for comparing theamplitude of two voltages approximately 90 out of phase. In accordancewith an aspect of my invention, this is accomplished by translating thedifference of amplitude between said voltages into a difference of phaseand measuring the difference of phase.

Other and further objects of the present invention will become apparentand my invention will be best understood from .the following descriptionof embodiments thereof, reference being had to the drawings, in which:

Fig. 1 is a schematic and block diagram of an electrical systemembodying my invention;

Figs. l2 and 3 are vector diagrams used in describing my invention;

Fig. 4 is a schematic and block diagramof a direction nder embodying myinvention; and

Fig. 5 is a polar diagram of the radiant reception pattern, of theantenna system of Fig. 4.

Referring now to Fig. l, energies from two sources of energy l and 2 areto be compared to determine the relative amplitude. This comparison isnot made directly but, in accordance with my invention, is accomplishedby translating the diiierence between the amplitudes of these energiesinto corresponding dilerences n phase and then comparing the differentphases. This translation of differences of amplitude into difierences ofphase is accomplished in a transmission line bridge or network 4, whichmay be of any suitable type, such as for example described in Patent No.2,147,809, granted to Andrew Alford, February 21, 1939. In making thistranslation from amplitude differences to corresponding phasedifferences, however, the energy from the two sources must be out ofphase and if sources l and 2 are in phase, this phase variation isaccomplished by means of a phase shifter 3 in series with one of saidsources, for example, source 2.

The transmission line bridge 4 illustrated is in the form of a closedloop of dual transmission line provided with a transposition asindicated in arm 5 of the bridge, and having two pairs of oppositeterminals 6 and 1, and 9 and 9, one pair 6 and 'l being at right anglesto the other pair 8 and 9. Each terminal consists of connections to eachconductor of the dual transmission line. Source I is connected toterminal 8, while the output of the 90 phase shifter 3 is connected toterminal 9. The voltages applied to terminal 8 will be divided equallyand appear at terminals E and '1. Likewise the voltages app-lied totermina] 9 will be divided equally and will appear at terminals B and 1.Thus at one of the terminals 6 and l, the voltages derived fromterminals 8 and 9 will add and at the other one of the terminals 6 and1, the voltages derived from terminals 8 and 9 will subtract, due to thetransposition. This will be better understood in connection with thevector diagrams of Figs. 2 and 3.

Let the voltages at terminals 6, 1, 8, and 9 be designated by thesymbols Ea, Et, E'a and E9 respectively. Assuming for the vector diagramof Fig. 2 that the voltages Es and E9 are equal, and `that at terminal 6a half of Es and a half of E9 add. while .at terminals 1, a half of Esplus a half -of E9 Subtract, the following results will be ob` tained,reference being had to Fig. 2.

At terminals Es, one-half of the volt-age Ea will be added to one-halfof the voltage E9, which latter voltage is 90 out of phase with theformer. Consequently Athe resultant voltage Es will be obtained atterminal S. At terminal 1, one-half the voltage Ea is combined with halfthe voltage E9, but since the voltage E9 is transposed or shifted 180,the resultant voltage appearing at terminal 'I will be as illustrated bythe vector E7 in Fig. 2. Voltage Ea is equal to voltage E7 but is out ofphase with it. The phase relation between the voltages at terminals 6and 1, is indicated by the angle p in Fig. 2 and will be 90 when thevoltages Ea and E9 are equal and the bridge is perfectly symmetrical.Assuming, however, as in the vector diagram of Fig. 3 that the amplitudeof the voltages applied'tov terminals 8 is less than that applied toterminal 9, the angle p will change and as can be seen from Fig. 3 aphase angle e will be obtained between the voltages at terminals 6 and1, which is larger than 90. Likewise it can be shown that if the voltageat terminal 3 is less than kthe voltage at terminal 8, a smaller phaseangle less'than 90, will be obtained between the voltages at terminals 6and 'I. vIt will therefore be seen thatk the phase angle of the voltagesappearing at terminals 8 and 'I will vary in accordance with thediierence inam-plitude between the voltages applied to terminals 8 and9.

If when the resultant phase of the voltages at terminals 6 and 'I arecompared as in any suitable phase comparison device I and the dierenceof said phase is read on a suitably calibrated indicator II, thedifference in amplitude between the voltages derived from source I andthose derived -from source 2 is thus readily determined.

Of course it will be understood that if sources I and 2 are 90 out ofphase with each other, the phase shifter 3 becomes unnecessary.VOrdinarily where the amplitude of energy from two sources 90 out ofphase is to be compared, various diiiiculties are presented. Thissituation is very readily handled in accordance with the method andmeans hereinbefore described. An example of this is illustrated in thedirection finder system of Fig. 4.

Referring now to Fig. 4, a pair of vertical dipoles I2 and I3 arearranged in front of a reflector I4 and spaced apart a distance S whichis preferably small in respect to a wavelength, for example, 45 or less.Dipoles I2 and I3 are crossconnected by a transmission line I5 having atransposition I6 and a transmission line I'I is connected to themidpoint of line I5, the transmission line I'l being connected toterminal 8 of transmission line bridge 4. Dipoles I2 and I3 are arrangeda horizontal distance apart S They produce a radiant reception patternas indicated in dotted lines in Fig. 5 and designated by the numeral I8.This pattern has a null for energy being received in a plane normal tothe common plane of dipoles I 2 and I3. The pattern I8 has two lobes I9and 20 which are 180 out of phase with each other in terms of thevoltages `delivered to transmission line I1.

Another pair of similar vertical dipoles 2| and 22 is also mounted infront of the reflector I4, the l dipoles 2| and 22 being spaced apart adistance S" the same as the distance S separating dipoles I2 and I3. Thedipoles 2| and 22 are vertically spaced from each other and dipoles 2|and 22 exvdipole 22 be seen that the dipole arrangement is symmetrical.Dipoles 2| and 22 are connected together by a transmission line 24,which, however, has no cross-over. The midpoint of line 24 is connectedby a transmission line 25 to terminal 9 of the bridge 4.

Dipoles 2| and 22 have a radiant reception pattern as indicated in Fig.5 and designated by the numeral 26. Energy received according to pattern2B by dipoles 2| and 22 and applied to terminals 9, will be out of phasewith energy derived from dipoles I2 and I3 and applied to terminal 8.Accordingly, it willy be seen that the voltages applied to terminals 8and 9 are 90 out of phase which is the situation described in connectionwith the system of Fig. 1. Accordv ingly it will be readily apparentthat asthe amplitude of the voltages applied to terminals 8 and 9 vary,the phase of the voltages appearing at terminals 6 and 1 willcorrespondingly vary. Since there are two different vdirective patterns26 and I8, said amplitudes will vary in accordance with the patterns asthe direction from which energy is being received varies. Accordingly,when the resultant phase differences or phase variations are compared inany suitable phase comparison device, I0, and indicatedin any suitableindicator I I, the direction from which energy is being received willthen be indicated, upon suitable calibration of indicator II.

Any suitable phase comparison device and indicator may be employed suchas for example is described in my co-pending. application, N.Marchand-11, for "Phase control device, Serial No. 584,555, filed March24, 1945 or those described in my joint co-pending vapplication N.Marchand-M. Semel 12-1 for Phase comparison systems, Serial No. 578,741,filed February 19, 1945.

It will be recognized that the aforedescribed antenna array issymmetrical. Looking into transmission line I5 from dipole I2, not onlyis the impedance at the point at which transmission line II is connectedto transmission line I5 seen, but also the impedance of dipole I3. Asimilar relationship holds looking into dipole I3. Likewise looking intotransmission line 24 from dipole 2|, not only is the impedance of thepoint at which transmission line 25 is coupled to transmission line 24seen, but also the impedance of A similar relationship holds lookinginto pole 22. Accordingly, it will be seen that the impedances arebalanced and symmetrical in the system and this aids in producingaccurate direction findings and a balanced system.

Considering :the voltage applied to terminal 8 SO E8=jE sin (-2- sin 0)where E=1`.4 times the voltage received at each antenna connected to theterminal in question (1) 0=the angular direction of reception from thenormal plane.

Now, if the voltage at terminal 8 is split into -two parts and also thevoltage at terminal 9 is Two voltages will be obtained Es and E7 whereE=.5E+j.5E sin sin a) (s) E3:

E,=.5E-j.5E sin sin e) 4) E7:

The phase angle qb between Es and E7 is While I have described thespecific details of two embodiments of my invention, it will be apparentto those versed in the art that changes may be made in certain detailswithout departing from the teachings of my invention. For example, whileI have described the voltages applied to terminals and 9 as being 90out-ofphase, it will be apparent that this phase relationship may bevaried to a certain extent and in many instances no harm will resulttherefrom. Furthermore, while I have described the use of my inventionin connection with one type of antenna system, it will be apparent tothose versed in the art that it may be employed with many types ofantenna systems and many types of direction finders. Accordingly, whileI have described above the principles of my invention in connection withspecific apparatus, and particular modifications thereof, it is to beclearly understood that this description is made only by way of exampleand not as a limitation on the scope of my invention as defined in theaccompanying claims.

I claim:

1. A system for translating the relative amplitude -of energy derivedfrom two sources whose outputs are 90 out of phase with each other intodiierences in phase comprising a transmission line bridge having twopairs of opposite terminals and means eifectively producing an 180relative phase shift in one arm of said bridge, means separatelycoupling said sources to the terminals of one of said pairs and outputmeans coupled to each of the other terminals of the other of said pairs.

2. A system for comparing the relative amplitude of energy derived fromtwo sources whose outputs are 90 out of phase with each other comprisinga transmission line bridge having two pairs of opposite terminals andmeans effectively producing an 180 relative phase shift in one arm ofsaid bridge, means separately coupling said sources to the terminals ofone of said pairs, and phase comparison means coupled to the terminalsof the other of said pairs.

3. A system for comparing the relative amplitude of energy derived fromtwo sources whose outputs are in phase comprising means for shifting thephase of energy from one of said sources approximately 90 with respectto the other, a transmission line bridge having two pairs of oppositeterminals and means for eiectively producing an 180 phase shift in saidbridge, means separately coupling the energy derived from said twosources which have been shifted approximately in relationship to eachother to the terminals of one of said pairs, and phase comparison meanscoupled to the terminals of the other of said pairs.

4. A method of comparing the relative ampli` tudes of separateelectrical energy 90 out of phase by the use of a transmission linebridge having two pairs of opposite terminals and means producing aphase shift in one arm of said bridge, comprising applying the energiesto be compared separately to the opposite terminals of one of saidpairs, and comparing the phases between the energy appearing at theopposite terminals of the other of said pairs.

5. A direction nder comprising an antenna system having two diiferentdirective patterns, the energy received according to one pattern being90 out of phase with the energy received according to the other pattern,a transmission line `bridge having two pairs of opposite terminals andmeans for effectively producing an 180 phase shift in one of the arms ofsaid bridge,-means coupling the energy derived according to one of saidpatterns to one terminal of one of said pairs, means coupling the energyderived according to the other of said patterns to the opposite terminalof said one of said pairs, a phase-comparison device associated with anindicator, and means coupling the other pair of terminals to saidphasecomparison device.

6. A direction finder according to claim 5 wherein the antenna systemcomprises two pair of spaced vertical dipoles, a first pair being hori-`zontally spaced `from each other a given distance and the second pairbeing vertically spaced from each other an equal distance, all of saiddipoles being symmetrically disposed about a central point andequi-distant therefrom, a first transmission line interconnecting saidiirst pair of dipoles and having a cross-over therein, a secondtransmission line interconnecting said second pair of dipoles, theoutput from each of said transmission lines being taken off at themidpoint thereof.

7. A direction finder according to claim 5 wherein the vantenna systemcomprises two pair of spaced vertical dipoles, a rst pair beinghorizontally spaced from each other a given distance and the second pairbeing vertically spaced from each other an equal distance, all of saidydipoles being symmetrically disposed about a central point andequi-distant therefrom, a first transmission line interconnecting saidrst pair of dipoles and having a cross-over therein, a secondtransmission line interconnecting said second pair of dipoles, theoutput from each of said transmission lines being taken off at themidpoint thereof and further including `a planar reflector in front ofwhich all of said dipoles are mounted.

NATHAN MARCHAND.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS

